What do I do with this? Lol

Okay y’all, I loveee my husband. He’s the greatest guy. He can be a little particular though and he has a serious issue with my sister’s boyfriend. It’s driving me INSANE. His reason for not liking him is that “he’s a know it all”- says my husband, the King of Know It Alls 😂 now, I don’t mean that disrespectfully, my husband is a Jack of all trades and has more information in one small space of his brain than most people do in their entire brain. He really does know a lot more than most people, and he’s right 98% of the time too. But I almost wonder if he feels threatened or insecure around my sis’s bf for some reason? He always says how much he doesn’t like him, and it gets to the point where he will purposely shut down and refuse to talk to people at holiday/family functions because he’s in such a bad mood that he has to be in close proximity to the guy. I feel like he’s being a tad ridiculous. The guy is perfectly decent, he’s kind, respectful as far as I’ve ever seen, treats my sister well, is kind to our kids, heck he even plays with them if they try to involve him in a game of tag and etc. I have asked my husband about it but he just says the same thing, he doesn’t like him because he’s a know it all. And it really bothers me! It’s gotten to the point where his mood is so bad if my sis’s bf is around that I practically don’t get to see my sister and I’m not sure how to deal with this. Lol. Especially cause they are talking about getting married! I am very close with my sister too. Any thoughts? Am I being too hard on my husband?